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Reports until 09:27, Sunday 25 October 2015
H1 General
cheryl.vorvick@LIGO.ORG - posted 09:27, Sunday 25 October 2015 - last comment - 10:16, Sunday 25 October 2015(22811)
Ops Day Transition: IFO 2nd harmonic of violin modes is preventing Low Noise, Sheila and Elli on their way in

Ops Day Shift - 15:00-23:00UTC, 8:00-12:00PT, all times listed are UTC

H1: cannot get back to Low noise due to violin second harmonics around 1008Hz

Current Plans:

- Elli on her way in to do her measurement - takes about 30 minutes and she needs an unlocke IFO

- Sheila on her way in - she had me comment out the line that engages ETMY L2 MODE3 in the ISC Guardian, but suspects that that won't be enough to get back to Low Noise, so is driving in

Changes:

- ETMY L2 MODE3 in the ISC Guardian commented out, and I left a comment in the file that I did this today

Current state of ground motion:

- useism coming up again and upper data points are touching 1 on the seismic plot

- also some anthropogenic noise starting about one hour ago

Comments related to this report
cheryl.vorvick@LIGO.ORG - 09:32, Sunday 25 October 2015 (22812)
Link

The ROLL modes are quite bad, and I believe prevent IFO from getting to ENGAGE ASC

- Only time IFO has made it ENGAGE ASC this morning was when I turned on ROLL mode damping early

daniel.hoak@LIGO.ORG - 10:16, Sunday 25 October 2015 (22813)
Link 

It should be possible to construct two narrow filters to damp the violin modes - each perhaps 20mHz wide, centered on the line you want to damp. Filters this narrow should be able to damp one line without ringing up the other. From there it's just a matter of finding the right phase. Don't be too timid with the gain - i think using 30% of the DAC range is perfectly safe, once you are confident your settings won't ring anything else up. The higher harmonics need lots of gain.



In the past these modes have damped very easily. The settings have been stable for months - I wonder what changed?
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